1. Field of the Invention
The present invention relates to cervical plate systems and methods, more specifically, a cervical plate system that provides retention of a bone fixation element wherein vertical movement of the bone fixation element is significantly reduced.
2. Description of Related Art
Cervical spine surgery is a neurosurgical procedure for treating a wide variety of cervical spine disorders and deformities, including, but not limited to, cervical deformation, disc degeneration, arthritis, and congenital defects. In addition, cervical spine surgery is utilized to treat cervical fractures, injuries, or other traumas to the spine wherein the spine becomes displaced or otherwise altered from such fracture, injury, or trauma.
The procedure utilizes synthetic devices to anchor two or more vertebrae to one another in the spinal column. Such devices may include bone fixation elements, also referred to as bone screws, coupled to a fixation plate. The bone fixation elements are positioned within apertures located in the fixation plate are driven into the desired vertebrae. Such devices are typically temporary devices used to stabilize bone fragments or bones to one another until the fragments heal and/or the bones are fused to one another. As the ultimate goal of utilizing such synthetic devices is to limit movement of the cervical spine to promote healing, it is of great importance that fixation between the bone fixation element and fixation plate be secure.
Various structures for securing fixation plates to vertebrae are currently available wherein bone fixation elements are inserted through apertures located in the fixation plate and driven into the vertebrae. A problem associated with utilizing such bone fixation elements in cervical plate systems, however, is “backing out” wherein movement of the bone fixation element(s) occur. Such backing out may be in reference to movement of the bone fixation element in a vertical, horizontal, lateral, rotational, or any other direction of movement post-insertion of the bone fixation element into the bone.
To minimize such movement, various cervical plate systems include the use of locking plates wherein the locking plate is adjusted so as to cover the head of the bone fixation element once the bone fixation element has been inserted into the bone. In this manner, vertical movement of the bone fixation element is limited due to the head of the bone fixation element abutting the locking plate. Although use of a locking plate that covers the head of the bone fixation element prevents vertical backing out of the bone fixation element to a certain degree, vertical backing out is possible if there exists a distance between the top surface of the head of the bone fixation element and the bottom surface of the locking plate adjacent to the bone fixation element head. Moreover, locking plates that cover the head of the bone fixation element may not prevent or minimize backing out in other directions, such as horizontal, lateral, rotational, or other directional movement of the bone fixation element.
Thus there exists a need for an improved cervical plate system that minimizes movement of a bone fixation element after its insertion into the bone.